Inkjet recording apparatus and recording method

ABSTRACT

An inkjet recording apparatus includes a recording head having a nozzle row aligned with a plurality of nozzles and a carrying mechanism capable of carrying a record medium by a multiple of an arbitrary natural number of a unit carry amount in a direction in parallel with the nozzle row. The record medium is carried by any of quasi logical carry amounts including a natural number larger than a logical carry amount determined based on a recording resolution and a number of nozzles and represented as a multiple of the unit carry amount and a natural number smaller than the logical carry amount. The record medium is recorded at each time of carrying the record medium. A carry amount of the record medium is determined such that a difference between the logical carry amount and an actual carry amount of the record medium does not exceed a predetermined value.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an inkjet recording apparatus whichperforms recording on a record medium that is carried in a direction inparallel with a direction of aligning nozzles by a recording head formedwith the nozzles, and to a recording method for use in the inkjetrecording apparatus.

2. Description of the Related Art

There is known an inkjet recording apparatus that performs recording byejecting ink to a record sheet. As the inkjet recording apparatus, aserial type in which a recording head having a nozzle row aligned with aplurality of nozzles for ejecting ink in one direction at a constantpitch (pitch corresponding to nozzle resolution) is attached to acarriage reciprocated in a direction orthogonal to the nozzle aligningdirection is generally used. As disclosed in JP-A-2000-15867, accordingto the inkjet recording apparatus of the serial type, a recordingmechanism carries a record sheet in a nozzle aligning direction(hereinafter, referred to as “sub-scanning direction”) in synchronismwith reciprocating the carriage in a direction orthogonal to the nozzlealigning direction (hereinafter, referred to as “main scanningdirection”). In this case, the carrying mechanism can carry the recordsheet in the sub-scanning direction by a unit carrying amountconstituting a minimum carrying amount thereof (for example, a carryingamount corresponding to 2400[dpi]) multiplied by a natural number.

SUMMARY OF THE INVENTION

When a record sheet is recorded by using the above-described inkjetrecording apparatus, if the sheet carrying resolution (hereinafter,referred to as “recording resolution”) in the sub-scanning direction bythe carrying mechanism is increased, the record sheet can be recordedwith the higher image quality such that a cross streak (also called as“banding”) is prevented from being brought about. Further, since animage is formed by driving the nozzle in the main scanning directionwhile carrying the record sheet in the sub-scanning direction, therecording resolution in the sub-scanning direction becomes to be thenozzle resolution multiplied by a natural number. Actually, it isgeneral to prepare a plurality of record resolutions such that a usercan pertinently select a desired recording resolution from variousrecording resolutions. Furthermore, even when the plurality of recordingresolutions are prepared in this way, in order to reduce costs formanufacturing the whole apparatus, it is general to use the same partfor a sensor of an encoder or the like for controlling an accuracy ofcarrying by the carrying mechanism. Therefore, a minimum resolution of acarrying function which can be controlled by utilizing the encoder orthe like (that is, an inverse number of the unit carrying amount and ishereinafter referred to as “unit carrying resolution”) is related to theplurality of recording resolutions to be a value of a least commonmultiple of the plurality of recording resolutions multiplied by anatural number. Further, in order to prevent the above-described leastcommon multiple from being considerably a large value, a plurality ofrecording resolutions are set to be values multiplied by an exponent of2 thereamong.

Specifically, there is a case in which with respect to the nozzleresolution of 75[dpi], the recording resolution in the sub-scanningdirection is set to 150[dpi] that is 2 times of 75[dpi], 300[dpi] thatis 4 times of 75[dpi], 600[dpi] that is 8 times of 75[dpi], and1,200[dpi] that is 16 times of 75[dpi]. Further, the unit carryingresolution of the encoder or the like at this occasion is set to6,000[dpi] that is 5 times of a least common multiple of 1,200[dpi] ofthe respective recording resolutions.

Assuming that there is not the above-described relationship(relationship of being multiplied by an exponent of 2) (when, forexample, 750[dpi] that is 10 times of a nozzle resolution, 2,400[dpi]that is 32 times thereof, and 6,000[dpi] that is 80 times thereof aremixed as recording resolutions in the sub-scanning direction), a minimumcommon multiple thereof becomes 480,000[dpi] to reach a level at which amechanism of achieving the accuracy cannot be constructed in fact.

Therefore, in a product of a related art, there are frequently cases inwhich only resolutions in the sub-scanning direction having arelationship of being multiplied by an exponent of 2 can be selected.

Further, the above-described restriction also brings about a drawback asfollows. When a higher resolution is needed in order to promote an imagequality, the resolution is obliged to be 2 times of the highestrecording resolution in a current state. Further, when the highestrecording resolution becomes 2 times of the resolution, a unit carryingresolution in the carrying mechanism also needs to be multiplied by 2 inaccordance therewith. However, the carrying mechanism having the highunit carrying resolution constitutes a factor of high cost.

Further, assuming that a time period necessary for one time mainscanning recording stays the same, a carrying time period in thesub-scanning direction is needed by twice as much as a time periodnecessary for recording simply. Therefore, when it is assumed that atime period necessary for recording an image on one sheet of A4 size bythe current maximum recording resolution is 2 minutes, in the case ofdoubling the recording resolution, 4 minutes are needed and a longperiod of time is required until finishing to record an image.

On the other hand, it is said that perception and sensitivity of humanbeing execute logarithmic response to a stimulating amount. That is,even a time period of recording an image is doubled, the human beingdoes not frequently regard that the image quality is improveddouble-fold. In this way, the sensitivity of the human being isfrequently ambiguous. Therefore, as a trade-off design of the imagequality and the recording time period in implementing a product, it isintended to delicately adjust the both factors, however, in the relatedart, it is necessary to provide the resolution in the sub-scanningdirection with a value of an exponent of 2 and therefore, such adelicate adjustment cannot be carried out.

The present invention provides an inkjet recording apparatus beingcapable of using a recording resolution that can realize to record witha high image quality without bringing about high cost for producing acarrying mechanism and without considerably reducing a recording speed.

According to one aspect of the invention, there is provided an inkjetrecording apparatus including: a recording head having a nozzle rowaligned with a plurality of nozzles for ejecting ink; a carryingmechanism being capable of carrying a record medium by a multiple of anarbitrary natural number of a unit carrying amount in a direction inparallel with the nozzle row; a carry controlling unit that controls thecarrying mechanism such that the record medium is carried by any of aplurality of quasi logical carry amounts including a natural numberlarger than a logical carry amount, which is determined based on arecording resolution along the direction in parallel with the nozzle rowand a number of nozzles that are used for recording in the nozzle rowand is indicated as a multiple of the unit carrying amount, and anatural number smaller than the logical carry amount; and a recordinghead controlling unit that controls the recording head such that therecord medium is recorded at each time of carrying the record medium bythe carrying mechanism that is controlled by the carry controlling unit.The carry controlling unit determines a carry amount of the recordmedium by the carrying mechanism from the plurality of quasi logicalcarry amounts such that a difference between a carry amount when therecord medium is assumed to be carried by the logical carry amount andan actual carry amount of the record medium does not exceed apredetermined value.

According to another aspect of the invention, there is provided arecording method for use in an inkjet recording apparatus including arecording head having a nozzle row aligned with a plurality of nozzlesfor ejecting ink, and a carrying mechanism being capable of carrying arecord medium by a multiple of an arbitrary natural number of a unitcarry amount in a direction in parallel with the nozzle row, therecording method including: carrying the record medium by a single or aplurality of times by the carrying mechanism by any of a plurality ofquasi logical carry amounts including a natural number larger than alogical carry amount, which is determined based on a recordingresolution along the direction in parallel with the nozzle row and anumber of the nozzles that are used for recording in the nozzle row andis indicating a rate relative to the unit carry amount in the carryingmechanism, and a natural number smaller than the logical carry amount;and recording the record medium by the recording head after thecarrying. In the carrying, the record medium is carried by a carryamount such that a difference between a carry amount by which the recordmedium is assumed to be carried by the logical carry amount and anactual carry amount of the record medium does not exceed a predeterminedvalue.

According to the aspects of the invention, recording can be executedwithout constituting the recording resolution by a multiple of the unitcarrying resolution. Therefore, the recording resolution capable ofrealizing high image quality recording can be used without using acarrying mechanism at high cost having a high unit carrying resolutionand without considerably reducing a recording speed. Further, since therecording resolution may not be a multiple of the unit carryingresolution, a relationship of a multiple of an exponent of 2 may not beprovided between the resolutions. Therefore, a delicate balance can beadjusted between a printing time period and an improvement in an imagequality and a product specification having excellent handlingperformance for a user can be proposed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be more readily described with reference tothe accompanying drawings:

FIG. 1 is a perspective view showing a constitution of a multifunctionmachine;

FIG. 2 is an explanatory view showing a constitution of an inkjetprinter;

FIG. 3 is an explanatory view showing the constitution of the inkjetprinter;

FIGS. 4A and 4B illustrate explanatory views showing operation of arecording head;

FIG. 5 is a block diagram showing an electric constitution of the inkjetprinter;

FIG. 6 shows data stored to a carry amount corresponding data storingportion;

FIG. 7 shows data stored to a logical carry amount storing portion;

FIG. 8 shows data stored to a quasi logical carry amount storingportion;

FIG. 9 is a flowchart showing a processing of calculating a logicalcarry amount;

FIG. 10 is a flowchart showing a processing of generating print data;

FIG. 11 is a flowchart showing a dot data converting processing;

FIG. 12 is a flowchart showing a processing of driving a sheet feedingmotor and a recording head;

FIG. 13 is a flowchart showing a processing in a first mode;

FIG. 14 is a flowchart showing a processing in a second mode;

FIG. 15 is a view showing a mode of recording dots on a sheet;

FIG. 16 shows data indicating a difference between the logical carryamount and an amount by which a sheet is actually carried which arerelated to a number of times of carrying the sheet;

FIGS. 17A to 17C illustrate views showing a relationship between a shiftof a position of a dot and production of a gap;

FIG. 18 is an explanatory view showing a matrix used in the dot dataconverting processing;

FIG. 19 is an explanatory view showing a state of aligning a dot on asheet;

FIG. 20 is an explanatory view of a visibility limit resolution;

FIG. 21 is a modified example of a block diagram showing an electricconstitution of an inkjet printer; and

FIG. 22 is a block diagram showing an electric constitution of amultifunction machine according to a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An explanation will be given of a first embodiment and a secondembodiment of an inkjet recording apparatus according to the inventionwith reference to the drawings as follows.

First, a total constitution of a multifunction machine according to thefirst embodiment will be described in reference to FIG. 1. Amultifunction machine 1 is provided with a sheet feeding apparatus 2 ata rear end portion thereof, provided with an original reading apparatus3 for a copy function or the like on an upper side of a front side ofthe sheet feeding apparatus 2, and is provided with an inkjet printer(inkjet recording apparatus) 4 for realizing a printer function or thelike at a total of a lower side of the draft reading apparatus 3. Afront side of the inkjet printer 4 is provided with a sheet dischargingtable 5 for a sheet recorded with an image. Further, an upper face of afront side of the inkjet printer 4 is provided with LCD 74 capable ofdisplaying set information or the like.

Next, a constitution of the inkjet printer 4 will be described inreference to FIG. 2 through FIG. 4.

The inkjet printer 4 includes a record mechanism portion 10 forrecording an image on a sheet supplied from the sheet feeding apparatus2 (for example, sheet of A4 size or letter size) by a recording head23P, a maintenance mechanism portion 11 for executing a maintenanceprocessing of the recording head 23P, an ink supply portion 12 forsupplying ink from ink cartridges 40 through 43 to the recordingmechanism portion 10, a pressurized air supply portion 13 for supplyingpressurized air to the ink cartridges 40 through 43 and the like.

The recording mechanism portion 10 is contained in a recording unitframe 20 in a shape of a flat box including a reinforcement ceilingplate provided with an opening portion that permits access to a sheet.Both left and right end portions of a guide shaft 21 on a rear side anda guide rail 22 on a front side in the frame 20 are respectively fixedby a right side wall 20 a and a left side wall 20 b, a carriage 23 andthe recording head 23P are guided and supported by the guide shaft 21and the guide rail 22 movably in a left and right direction, and can bereciprocated in the left and right direction along the guide shaft 21and the guide rail 22 by a carriage drive motor 24 via a timing belt.Further, the recording head 23P is fixedly connected to a front end sideof the carriage 23, the carriage 23 is guided by the guide shaft 21 andthe recording head 23P is guided by the guide rail 22.

A lower face of the recording head 23P is provided with four rows ofinkjet nozzle rows 23 a through 23 d corresponding to four colors of inkcolors, and each nozzle row is provided with a number of inkjet nozzles.The nozzle row 23 a for black and the nozzle row 23 b for cyan areproximate to each other and the nozzle row 23 c for magenta and thenozzle row 23 d for yellow are proximate to each other. When therecording head 23P is scanned in the main scanning direction as shown byan arrow mark of FIG. 4A, the recording head 23P forms a dot on a sheetby ejecting an ink drop by being driven by a piezoelectric actuator. Asshown in FIG. 4B, the recording head 23P forms an image on a sheet P byalternately repeating scanning in the main scanning direction (arrowmarks 1, 3, 5) and scanning in the sub-scanning direction (arrow marks2, 4) relative to the sheet. However, actually, the recording head 23Pis not moved in the sub-scanning direction and the sheet is fed in thesub-scanning direction. Further, the recording head 23P may be arecording head of a heat generating element drive type.

A lower side of the guide shaft 21 is arranged with a main carry roller(not illustrated) to be respectively rotatably and axially supported,rotated in a predetermined rotational direction by a sheet feed motor 26via a gear mechanism 27, carries a sheet fed from the sheet feedingapparatus 2 in a front sheet feeding direction while moving the sheetsubstantially horizontally on immediately lower side of the recordinghead 23P, and discharges the sheet onto the sheet discharging table 5.

The maintenance mechanism portion 11 is provided with a maintenance case30 at a vicinity of a bottom portion of a right end portion in therecord unit frame 20.

A front side of the ink supply portion 12 is arranged with the inkcartridge 40 of black, the ink cartridge 41 of cyan, the ink cartridge42 of magenta, and the ink cartridge 43 of yellow successively from aleft side in respectives of the ink cartridges 40 through 43. Insides ofcartridge cases are expanded with flexible film members 40 a through 43a substantially over entire regions thereof, and by the film members 40a through 43 a, the cartridge cases are partitioned into ink containingchambers 40 b through 43 b on a lower side and air chambers 40 c through43 c on an upper side. Respective inks are contained in the inkcontaining chambers 40 b through 43 b, and atmospheric air flows intothe air chambers 40 c through 43 c. Black ink BI, cyan ink CI, magentaink MI, and yellow ink YI are respectively contained in the inkcontaining chambers 40 b through 43 b of the ink cartridges 40 through43.

Ink needles 44 are provided in a frontward projected shape respectivelyon depth sides of mounting portions for mounting the ink cartridges 40through 43. Base end portions of the respective ink needles 44 areconnected to the recording head 23P via corresponding exclusive inksupply tubes 45 through 48. The ink supply tubes 45, 46 are bundled tooverlap in an up and down direction from middle portions thereof andalso the ink supply tubes 47, 48 are bundled to overlap in the up anddown direction from middle portions thereof.

The recording head 23P is arranged at a position higher than the inkcartridges 40 through 43 by a predetermined water head difference, andwhen the ink cartridges 40 through 43 are respectively mounted to thepredetermined mounting portions, front end portions of the ink needles44 insert through rear end portions of the film members 40 a through 43a to reach the ink containing chambers 40 b through 43 b, and inks BI,CI, MI, YI of the ink containing chambers 40 b through 43 b are suppliedto the recording head 23P by way of the ink supply tubes 45 through 48.In this way, nozzles 23 n of the nozzles rows 23 a through 23 d of therecording head 23P are filled with inks BI, CI, MI, YI supplied by wayof the ink supply tubes 45 through 48.

Next, an electric constitution of the inkjet printer 4 will be describedin reference to a block diagram of FIG. 5 and FIG. 6 through FIG. 8.

The inkjet printer 4 is provided with CPU 51, RAM 58, ROM 61, which areconnected to each other by buses, not illustrated. ROM 61 is stored withvarious data for functioning CPU 51. Further specifically, ROM 61 isprovided with a record data generating program storing portion 62 storedwith programs for generating record data, a logical carry amountcalculating equation storing portion 63 stored with a calculatingequation of a sheet carry amount (hereinafter, referred to as “logicalcarry amount”) P per time necessary for recording an image on the recordmedium with a desired recording resolution d, and a carry amountcorresponding data storing portion 64 stored with data for calculatingquasi logical carry amounts P1, P2 for actually carrying a sheet whenthe logical carry amount P is not a natural number. Further, the carryamount corresponding data is data illustrated in FIG. 6 and is storedwith a first quasi logical carry amount P1 and a second quasi logicalcarry amount P2 which are related to a range of the logical carry amountP. Specifically, the first quasi logical carry amount P1 is the largestnatural number smaller than the logical carry amount P and the secondquasi logical carry amount P2 is the smallest natural number larger thanthe logical carry amount P.

CPU 51 is provided with a carry control portion 52, a record controlportion 53, a logical carry amount calculating portion 54 and a quasilogical carry amount calculating portion 55.

The carry control portion 52 carries a sheet by the logical carry amountP corresponding to the recording resolution d stored to a logical carryamount storing portion 59, or either of the quasi logical carry amountsP1, P2 stored to a quasi logical carry amount storing portion 60.Specifically, the carry control portion 52 calculates the logical carryamount P or the quasi carry amounts P1, P2 based on data stored toeither of the logical carry amount storing portion 59 and the quasilogical carry amount storing portion 60 of RAM 58, and drives to rotatethe sheet feed motor 26 via a motor driver 68 for carrying a sheet bythe calculated logical carry amount P or the calculated quasi logicalcarry amounts P1, P2. Here, the logical carry amount storing portion 59is stored with data illustrated in FIG. 7, that is, the logical carryamount P related to the recording resolution d. Further, the quasilogical carry amount storing portion 60 is stored with data illustratedin FIG. 8. Here, the data illustrated in FIG. 8 is stored with the firstquasi logical carry amount P1 and the second quasi logical carry amountP2 in a related manner to the logical carry amount P of a nonnaturalnumber in the data (refer to FIG. 7) stored to the logical carry amountstoring portion 59. Further, a rotating amount actually driven by thesheet feeding motor 26 is fed back by an encoder 67 attached to thesheet feeding motor 26.

The record control portion 53 functions as a record data generatingportion by the record data generating program when image data (imagedata) is transmitted from PC (personal computer) connected to themultifunction machine 1 via an image input portion 65 and generatesrecord data. The generated record data is transmitted to the recordinghead 23P via a head driver 69 and an image is formed on the sheet basedon the record data.

The logical carry amount calculating portion 54 calculates the logicalcarry amount P for recording an image by a desired recording resolutiond in a direction in parallel with the nozzle row aligned in therecording head 23P based on a logical carry amount calculating equation.Further, the calculating equation for calculating the logical carryamount P is a calculating equation calculated based on the recordingresolution d and a number M of nozzles used for recording in the nozzlerow of the recording head 23P and is represented by the followingEquationlogical carry amount P=number of nozzle M×unit carrying resolution ofencoder X/recording resolution d  (1)

Further, Equation (1) is derived as follows. First, a number ofrecording times (hereinafter, referred to as “Pass”) necessary forrecording a dot on a sheet by a desired recording resolution d by usingthe recording head 23P having a predetermined nozzle resolution V isrepresented by the following Equation (2).Pass=recording resolution d/nozzle resolution V  (2)

Further, a total length of the recording head 23P is represented by thefollowing Equation (3). $\begin{matrix}\begin{matrix}{\begin{matrix}{{recording}\quad{head}} \\{{total}\quad{length}}\end{matrix} = {{number}\quad{of}\quad{nozzle}\quad M \times {nozzle}\quad{interval}}} \\{= {{number}\quad{of}\quad{nozzle}\quad{M/{nozzle}}\quad{resolution}\quad V}}\end{matrix} & (3)\end{matrix}$

Here, a logical carry length p [inch) corresponding to the logical carryamount P [pulse) is a value constituted by dividing the total length ofthe recording head 23P by Pass, and the logical carry length p [dpi] isa value constituted by converting the logical carry length p [inch] intoa unit. The logical carry length p [inch] and the logical carry amount P[pulse] are represented as shown by Equation (4) shown below fromEquation (2) and Equation (3), described above. $\begin{matrix}\begin{matrix}{{{logical}\quad{carry}\quad{length}\quad p} = {{recording}\quad{head}\quad{total}\quad{{length}/{Pass}}}} \\{\begin{matrix}{{logical}\quad{carry}} \\{{amount}\quad P}\end{matrix} = {{logical}\quad{carry}\quad{length}\quad p \times}} \\{\quad{{unit}\quad{carrying}\quad{resolution}\quad{of}\quad{encoder}\quad X}} \\{\quad{= {{number}\quad{of}\quad{nozzle}\quad{M/{nozzle}}\quad{resolution}\quad{V/}}}} \\{\quad{( {{recording}\quad{resolution}\quad{d/{nozzle}}\quad{resolution}\quad V} ) \times}} \\{\quad{{unit}\quad{carrying}\quad{resolution}\quad{of}\quad{encoder}\quad X}} \\{\quad{= {{number}\quad{of}\quad{nozzle}\quad M \times {unit}\quad{carrying}\quad{resolution}}}} \\{\quad{{of}\quad{encoder}\quad{X/{recording}}\quad{resolution}\quad d}}\end{matrix} & (4)\end{matrix}$

In this way, Equation (1) is derived as the equation of representing thelogical carry amount P [pulse].

Here, the unit carrying resolution X of the encoder 67 will simply bedescribed. According to the embodiment, a rotary encoder is used for theencoder 67 and is disposed on a drive roller (not illustrated) connectedwith a sheet feeding motor. The rotary encoder 67 is formed with slitsat intervals of 300[dpi] at a circular disk having a diameter of 6/π[inch]. At an upper portion of the rotary encoder 67, two pieces ofoptical sensors for detecting presence or absence of the slit areprovided at positions shifted from each other to an extend thatcorresponds to 1,200[dpi]. By detecting the slits formed at the intervalof 300 [dpi] by two pieces of the optical sensors, there is achieved aresolution of 1,200[dpi] as a detecting capability which is four timesof the slit interval. Here, the unit carrying resolution X of theencoder 67 is calculated by “X=circumference×optical sensor resolution”.Therefore, when the slits at intervals of 300[dpi] formed on thecircumference of 6/π and two pieces of the optical sensors achieving theresolution of 1,200[dpi] are used, X=6/π×π×1,200=7,200[dpi] whichbecomes the resolution of the encoder 67 according to the embodiment.

The quasi logical carry amount calculating portion 55 calculates thecarry amount for actually carrying the sheet (first quasi logical carryamount P1 and second quasi logical carry amount P2) when the logicalcarry amount P is not a natural number. That is, a rotating amount pertime of the sheet feeding motor 26 becomes the unit pulse (unit carryingresolution X) of the encoder 67 having a predetermined resolution (unitcarrying resolution of encoder) multiplied by a natural number.Therefore, when the logical carry amount P is not a natural number, thesheet cannot be carried by an amount of the logical carry amount P whichis not a natural number. In this case, the quasi logical carry amountcalculating portion 55 calculates the carry amounts P1, P2 for actuallycarrying the sheet although difference amounts thereof from the logicalcarry amount P are produced.

Next, processing executed by CPU 51 of the inkjet printer 4 will bedescribed in reference to FIG. 9 through FIG. 14.

A flow shown in FIG. 9 is a flow for calculating the logical carryamount P. Calculation of the logical carry amount P is executed byinputting a change of the recording resolution d from a keyboard 66. Atstep 100, when a change of the recording resolution d is inputted, theoperation proceeds to step 101, and the logical carry amount calculatingportion 54 calculates the logical carry amount P by using Equation (1)stored at the logical carry amount calculating equation storing portion.At this occasion, when the change of the recording resolution d is notinputted, the change is set to a default value (for example, 1.200[dpi]). Further, at step 102, the calculated logical carry amount P isstored to the logical carry amount storing portion 59 of RAM 58.Incidentally, in this embodiment, the number of nozzle M is 13 pieces.

The operation proceeds to step 103, and it is determined whether thelogical carry amount P calculated at step 101 is a natural number. Here,when the logical carry amount P is a natural number, the logical carryamount calculating flow is finished. On the other hand, when thecalculated logical carry amount P is a nonnatural number, the operationproceeds to step 104 and calculates the first quasi logical carry amountP1 and the second quasi logical carry amount P2 based on data (refer toFIG. 6) stored to the carry amount corresponding data storing portion64. Further, at step 105, the calculated first quasi logical carryamount P1 and the calculated second quasi logical amount P2 are storedto the quasi logical carry amount storing portion of RAM 58 in a relatedmanner to the logical carry amount P (refer to FIG. 8) and thereafter,the logical carry amount calculating flow is finished.

At step 110 of FIG. 10, image data is inputted to CPU 51 via the imagedata input portion 65 (refer to FIG. 5). The image data is image data ofCMYK 4 colors system. Further, the image data may be image data of RGBsystem. Further, image data is data of 256 gray scales of 0 through 255.

At step 111, the image data is converted by a color convertingprocessing. Specifically, conversion is executed by LUT (Look-Up Table)conversion.

At step 112, dot data of 4 gray scales (4 gray scales of large dot,middle dot, small dot, not recorded) is generated from the image data of256 gray scales by a dot data generating processing. In the dot datagenerating processing, a half tone processing of a dithering processing,an error diffusing processing or the like is used.

At step 113, the dot data is converted by a dot converting dataprocessing. The converted dot data is made to constitute a print data.Further, the dot data converting processing will be described later indetails.

At step 114, the converted dot data is transmitted to the recording head23P as print data. The recording head 23P forms an image on a sheet byusing the print data.

Next, the dot data converting processing at step 113 will be describedin reference to a flowchart of FIG. 11.

At step 120, one line data L is read from dot data. The line data L isdata corresponding to one line along the main scanning direction.

At step 121, it is determined whether the recording resolution d in themain scanning direction of the read line data L is equal to or largerthan a threshold th. In the case of YES, the operation proceeds to step122 and in the case of NO, the operation proceeds to step 124. Here, thethreshold th is 508[dpi).

At step 122, a multi line processing is executed for the line data L.Here, the multi line processing refers to a processing of dividing 1piece of the line data L into 5 pieces of divided line data L1, L2, L3,L4, L5 based thereon.

The multi line processing is executed by multiplying the line data L bya mask M shown in FIG. 18. That is, by multiplying the line data L by amask M1, the divided line data L1 is generated. Similarly as follows,the divided line data L2 is generated by multiplying the line data L bya mask M2, the divided line data L3 is generated by multiplying the linedata L by a mask M3, the divided line data L4 is generated bymultiplying the line data L by a mask M4, and the divided line data L5is generated by multiplying the line data L by a mask M5. Further, themasks M1 through M5 are utilized such that L1(i)=M1(i%j)×L(i),L2(i)=M2(i%j)×L(i), L3(i)=M3(i%j)×L(i), L4(i)=M4(i%j)×L(i),L5(i)=M5(i%j)×L(i) and are repeatedly used in accordance with a datalength of the line data L. Here, notation i designates a dot number inthe main scanning direction, notation j designates data lengths of themasks M1 through M5, and notation % designates a function of rounding upa residue of (i/j).

Further, as shown in FIG. 19, a line of 1A is formed based on thedivided line data L1 divided from 1 piece of the line data L, a line of1B is formed based on the divided line date L2, a line of 1C is formedbased on the divided line data L3, a line of 1D is formed based on thedivided line data L4, and a line of 1E is formed based on the dividedline data L5. The same goes with the line data L thereafter. Further, apitch of contiguous lines of the respective divided line data L1, L2,L3, L4, L5 becomes H/5 and therefore, a length of an image in thesub-scanning direction is the same as that in a case of not dividing theline data L.

The masks M1 through M5 are constituted to constitute the line data Lwhen the respective divided line data L1 through L5 are added up. Thatis, the masks M1 through M5 are constituted such that in divided linedata Lk (k is 1 through 5), when an i-th dot in the main scanningdirection is designated by notation Lk(i), in the line data L, an i-thdot in the main scanning direction is designated by notation L(i), themasks M1 through M5 are constituted to constitute L(i)=εLk(i). As themasks M1 through M5, as shown in FIG. 18, an element of a matrix may beeither of 1 or 0 and a total of each row or each column of the matrixmay be 1.

At step 123, the divided line data L1 through L5 is outputted to therecording head 23P as print data.

On the other hand, when it is determined as NO at step 121, theoperation proceeds to step 124. At step 124, 1 piece of the line data Lis subjected to a single line processing for outputting 1 piece of theline data L as it is as print data (that is, substantially notconverted). At step 125, print data Q (substantially equivalent to theline data L) is outputted to the recording head 23P.

Next, FIG. 12 shows a control flow for controlling to record an image ona sheet by the inkjet printer 4 according to the embodiment, that is,for driving the sheet feeding motor 26 and the recording head 23P.

Incidentally, in this embodiment, a procedure of a processing executedby CPU 51 is indicated by “step” and indicated as “S” in the drawings.

At step 130, the inkjet printer 4 is at standby for inputting image datato CPU 51 via the image data input portion 65 (refer to FIG. 5). Whenimage data is received, the operation proceeds to step 131, the recordcontrol portion reads the logical carry amount P related to the setrecording resolution d based on data (refer to FIG. 7) stored to thelogical carry amount storing portion 59 of RAM 58. The operationproceeds to step 132, and the record control portion confirms whetherthe logical carry amount P calculated at step 131 is a natural number.When the logical carry amount P is a natural number, the operationproceeds to step 140, and the image is recorded on a sheet by a firstmode. On the other hand, when the logical carry amount P is a nonnaturalnumber, the operation proceeds to step 150 and the image is recorded ona sheet by a second mode.

A control flow of the first mode will be will be described in referenceto FIG. 13. Incidentally, a sheet is carried by controlling the sheetfeeding motor 26 by the carry control portion 52 based on a set carryamount R. At step 141, the logical carry amount P is set to the setcarry amount R. Thereafter, the operation proceeds to step 142, thesheet feeding motor 26 is driven to rotate by one time based on the setcarry amount R. Here, “one time” is a value of the unit carry amountmultiplied by a natural number. Further, when the sheet feeding motor 26is driven to rotate by one time, the sheet is fed by the set carryamount R. Further, when the sheet is fed by one time, the operationproceeds to step 143, and the record control portion 53 records an imageon the sheet. Here, when all of the image is not finished to record, theoperation returns to step 142 and when all the image has been finishedto record, the image by the first mode is finished to record.

A control flow in the second mode will be described in reference to FIG.14 through FIG. 16. Here, FIG. 14 is a diagram of a control flow, FIG.15 is a view representing a mode of recording a dot image on a sheet,and FIG. 16 shows data of a table showing a difference S between thelogical carry amount P and a carry amount (quasi logical carry amountsP1, P2) by which the sheet is actually carried for a carry number oftimes N. In this embodiment, the number of nozzle N is 13 pieces, thenozzle resolution V is V=600[dpi], the recording resolution d isd=6,000[dpi], and the unit carrying resolution X of the encoder is7,200[dpi]. Therefore, the logical carry amount P becomesP=15.6[pulses]. When P is 15.6, the quasi logical carry amounts P1, P2respectively become P1=15, P2=16 by data (refer to FIG. 6) stored to thecarry amount corresponding data storing portion 64. Further, similar tothe first mode, a sheet is carried by controlling the sheet feedingmotor 26 by the carry control portion 52 based on the set carry amountR.

In the second mode, the logical carry amount P is a nonnatural number,and therefore, the sheet is carried by either of the first quasicarrying amount P1 and the second quasi carry amount P2. Therefore, incarrying the sheet at a first time, there is produced the difference Sbetween a carry amount by which the sheet is to be carried (the logicalcarry amount P in carrying the sheet at the first time) T and the carryamount by which the sheet is actually carried (either of the first quasicarry amount P1 and the second quasi carry amount P2). Therefore, incarrying the sheet at a second time after carrying the sheet at thefirst time, it is necessary to carry the sheet by an amount of addingthe difference S (S=0.6) produced in carrying the sheet at the firsttime to the logical carry amount P. That is, the carry amount T by whichthe sheet is to be carried by carrying the sheet at an N-th time (N isan arbitrary natural number) becomes a sum of the difference S producedin carrying the sheet until an (N−1)th time and the logical carry amountP. Here, the difference S is a difference between the carry amount T bywhich the sheet is to be carried and the carry amount (set carry amount)R by which the sheet is actually carried.

First, at step 151, the logical carry amount P (P=15.6) is set as thecarry amount T by which the sheet is to be carried. The operationproceeds to step 152, the carry control portion 52 determines whetherthe carry amount T by which the sheet is to be carried is smaller thanthe second quasi logical carry amount P2 (P2=16). Here, when the carryamount T (T=P) by which the sheet is to be carried is smaller than thesecond quasi logical carry amount P2 (P2=16), the operation proceeds tostep 153 and the first quasi logical carry amount P1 (P1=15) is set asthe set carry amount R. On the other hand, when the carry amount T bywhich the sheet is to be carried is equal to or larger than the secondquasi logical carry amount P2, the operation proceeds to step 154, andthe second quasi logical carry amount P2 is set as the set carry amountR. Therefore, in carrying the sheet at a first time, the second quasilogical carry amount P1 (P1=15) is set as the set carry amount R.

When the set carry amount R is set, the operation proceeds to step 155,and the carry control portion 52 drives to rotate the sheet feedingmotor 26 by one time in order to carry the sheet by the set carry amountR. Thereby, the sheet is carried by R. Further, when the sheet iscarried by R, the operation proceeds to step 156, and the record controlportion 53 records an image on the sheet by controlling the recordinghead 23P via the head driver 69. The operation proceeds to step 157, andwhen all of the image has been finished to record, the image is finishedto record by the second mode and when all of the image has not beenfinished to record, the operation proceeds to step 158.

At step 158, the carry control portion 52 calculates the difference Sbetween the carry amount T by which the sheet is to be carried and themount (that is, the set carry amount) R by which the sheet is actuallycarried. According to the embodiment, for example, in carrying the sheetat the first time, the carry amount T by which the sheet is carried isset as the logical carry amount P, the first quasi logical carry amountP1 is set as the set carry amount R, respectively, and therefore, thedifference S between the logical carry amount P and the set carry amountR becomes S=0.6[pulse] (refer to FIG. 16).

After calculating the difference S between the carry amount T by whichthe sheet is to be carried and the set carry amount R, the operationproceeds to step 159, and the carry control portion 52 calculates thecarry amount T by which the sheet is to be carried in carrying the sheetat a succeeding time. Here, in carrying the sheet at the succeedingtime, the carry amount T by which the sheet is to be carried is a sum ofthe logical carry amount P and the difference S calculated at step 158.For example, the difference S calculated at step 158 in carrying thesheet at a first time is S=0.6[pulse] and therefore, the carry amount Tby which the sheet is to be carried in carrying the sheet at a secondtime is T=16.2[pulse] (refer to FIG. 16).

After calculating the carry amount T by which the sheet is to be carriedin carrying the sheet at the succeeding time at step 159, the operationreturns to step 152. Here, for example, in carrying the sheet at thesecond time, the carry amount T (T=16.2[pulse]) by which the sheet is tobe carried is larger than the second quasi logical carry amount P2(P2=16[pulses]) and therefore, the second quasi logical carry amount P2is set as the set carry amount R. In the following, the processing isexecuted by the above-described flow and at a time point of finishing tocarry the sheet at the second time, the difference S (S=0.2[pulse])calculated by the logical carry amount P and step 158 becomes smallerthan the difference S (S=0.6[pulse]) at a time point of finishing tocarry the sheet at the first time (refer to FIG. 16).

By repeating such series of processing, in the case of carrying thesheet by N times, a difference between a value of the logical carryamount P multiplied by N and an accumulated value of the carry amount(set carry amount) R by which the sheet is actually carried can beprevented from exceeding 1 [pulse]. At a time point of finishing torecord the image by the second mode, a difference between an accumulatedvalue of the carry amount R by which the sheet is actually carried andan accumulated value of the logical carry amount P can be reduced.

Further, in FIG. 15, consecutive numerals from 0 to 123 correspond todots for the desired recording resolution d. That is, a distance betweenrespective numerals becomes a value similar to the recording resolutiond. Further, circled numerals from 1 to 13 correspond to respectivenozzles for recording dots on the sheet. That is, since the number ofnozzle M is 13 pieces according to the embodiment and therefore, adistance between the respective circled numerals becomes a valuecorresponding to the nozzle resolution V. Here, in recording dots to thesheet by the recording head 23P, for example, in the case of a firstnozzle of a circled numeral 1, the nozzle records a dot at a position of0 after carrying the sheet at the first time and records a dot at aposition of 13 after carrying the sheet at the second time. An arrowmark illustrated in FIG. 15 indicates a distance between a position ofrecording a dot after carrying the sheet at an N-th time and a positionof recording a dot after carrying the sheet at an (N+1)-th time.Further, the arrow mark indicates a carry amount of carrying the sheetwhen the sheet feeding motor 26 is driven to rotate by one time andcorresponds to the carry amount shown in FIG. 16.

In this way, in the case of the inkjet printer 4 having the second mode,a dot image can be recorded on a sheet with the recording resolution dwhich is not a divisor of the unit carrying resolution X of the encoder67. Particularly, when the unit carrying resolution X of the encoder 67is equal to or larger than a visibility limit resolution W, it ispreferable that even when the difference S between the carry amount T bywhich the sheet is to be carried and the set carry amount R is produced,the difference S is not optically recognizable by the eye of the humanbeing. The visibility limit resolution W will be explained in referenceto FIG. 20 as follows.

The “visibility limit resolution” refers to a resolution of a limitrecognizable by the human being as a resolution on a sheet. The“visibility limit resolution” is determined by a distance (observationdistance) B between the eye E of the human being and a sheet Yillustrated in FIG. 20 and is represented by Equation (5) shown below.visibility limit resolution W=α/{tan (visibility limit field angleθ×π/180)×observation distance B}  (5)

-   -   where a coefficient α is a coefficient for converting a unit        from millimeter to inch, and notation θ designates the        visibility limit field angle.

According to “Fine image and hard copy” (edited by Corp. JapanPhotography Society, Japan Image Society issued by Corona Corp.), thevisibility limit field angle θ is determined to be θ=2 through10[seconds]. Further, the observation distance B depends on a size of asheet. For example, it is preferable that in the case of a sheet viewedfrom a remote distance such as a poster or the like, the observationdistance is set to B=5,000 μm] and in the case of A4 size, theobservation distance is set to B=250 μm].

According to the inkjet printer 4 of the embodiment, an image isrecorded frequently by A4 size and therefore, the observation distanceis set to B=250 μm]. Further, when the visibility limit field angle isset to θ=10[seconds], the visibility limit resolution W becomes nearlyequal to 2,001[dpi]. However, in order to achieve a higher imagequality, it is preferable to set the visibility limit field angle asθ=4[seconds], and the visibility limit resolution W in this case becomesnearly equal to 5,002. Further, in the case of a limit value of thevisibility field angle θ=2[seconds], W becomes nearly equal to10,000[dpi].

Therefore, the unit carrying resolution X of the encoder 67 used in theinkjet printer 4 is at least equal to or larger than 2,000[dpi], furtherpreferably, equal to or larger than 5,000 [dpi]. Further, when the unitcarrying resolution X of the encoder 67 is equal to or larger than10,000[dpi], it can be regarded that an error of an image is notrecognizable for most persons.

Incidentally, the first embodiment can be modified as follows. Forexample, the inkjet printer may be constructed by a constitution of ablock diagram illustrated in FIG. 21 in place of the block diagramillustrated in FIG. 5. Here, an inkjet printer 70 having a constitutionillustrated in FIG. 21 will be described. Further, elements havingconstitutions similar to those of the inkjet printer 4 having theconstitution illustrated in FIG. 5 are attached with the same notations.

The inkjet printer 70 is provided with CPU 71, RAM 72 and ROM 73.Although CPU 71 is provided with the carry control portion 52 and therecord control portion 53, CPU 71 is not provided with the logical carryamount calculating portion 54. Although the logical carry amount storingportion 59 and the quasi logical carry amount storing portion 60 areprovided not at RAM 73 but at ROM 61, ROM 61 is not provided with thelogical carry amount calculating equation storing portion 63 and thecarry amount corresponding data storing portion 64. That is, the inkjetprinter 70 having the constitution of the block diagram illustrated inFIG. 21 does not calculate the logical carry amount P and the quasilogical carry amounts P1, P2 but is stored with the logical carry amountP and the quasi carry amounts P1, P2 in a related manner to therecording resolution d. In this case, the recording resolution d ischanged by selecting any one of the recording resolutions d (refer toFIG. 7) previously stored to the logical carry amount storing portion59. Specifically, there are displayed the recording resolutions dcorresponding to multiples of the nozzle resolution V stored to thelogical carry amount storing portion 69 on LCD 74. Further, when adesired one of the recording resolution d is selected by the keyboard 66and the selected recording resolution d is determined (by depressing adetermination button provided at the keyboard 66 or the like), thedetermined resolution d is inputted to CPU 51. The recording resolutiond is set in this way. Further, when the recording resolution d is notchanged, the value is set to a default value (for example, 1,200[dpi]).In this way, although according to the inkjet printer 70 having theconstitution illustrated in FIG. 21, an arbitrary recording resolutioncannot be set, CPU 51 does not need to calculate the logical carryamount P and the quasi logical amounts P1, P2 and therefore, aprocessing burden is alleviated.

Next, an electric constitution of the multifunction machine according tothe second embodiment will be described in reference to FIG. 22.Further, constitutions having functions the same as those of the firstembodiment are attached with notations the same as notations attached tothe first embodiment.

As illustrated in FIG. 22, a multifunction machine (inkjet recordingapparatus) 80 is provided with CPU 51, ROM 61, RAM 58, the draft readingapparatus 3, the inkjet printer 4, the keyboard 66 and LCD 74. Further,the apparatus is connected with a PC interface portion (hereinafter,referred to as “PCI/F”) 82 for connecting with PC 81 via a communicationcable by way of a bus 83.

CPU 51 includes the carry control portion 51, the record controlportion, the logical carry amount calculating portion 54 and the quasilogical carry amount calculating portion 55 explained in the firstembodiment. RAM 58 includes the logical carry amount storing portion 59and the quasi logical carry amount storing portion 60 explained in thefirst embodiment. ROM 61 includes the record data generating programstoring portion 62, the logical carry amount calculating equationstoring portion 63 and the carry amount corresponding data storingportion 64. Further, although CPU 51, RAM 58 and ROM 61 control alsoother apparatus other than the inkjet printer 4 such as the draftreading apparatus 3 and therefore, strictly speaking, constitutionsthereof differ from those of CPU 51, RAM 58 and ROM 61 illustrated inthe first embodiment, those are attached with the same notations forconvenience.

The draft reading apparatus 3 reads a sheet set to the draft readingapparatus 3 by receiving an instruction from CPU 51 and generates imagedata of an image thereof.

The inkjet printer 3 records the image based on the image data for thesheet set to the sheet feeding apparatus 2 by receiving an instructionfrom CPU 51. Here, the image is recorded on the sheet by a processingprocedure similar to that explained in the first embodiment (refer toFIG. 12 through FIG. 16).

Further, there also is a case in which the multifunction machine 80 isinputted with image data from PC 81. When image data is inputted from PC81, CPU 51 transmits an instruction of recording an image to the inkjetprinter 80. The inkjet printer 3 records the image based on the imagedata to the sheet set to the sheet feeding apparatus 2 by receiving theinstruction instructing to record the image. Further, also in this case,the image is recorded on the sheet by a processing procedure similar tothat explained in the first embodiment (refer to FIG. 12 through FIG.16).

Although an explanation has been given of the first embodiment and thesecond embodiment as described above, the invention is not limited tothe above-described embodiments but designs thereof can variously bechanged. For example, although according to the above-describedembodiments, an explanation has been given of the case in which adifference between the first quasi carry amount P1 and the second quasicarry amount P2 becomes 1 which is the smallest value, the invention isnot limited thereto. For example, even when the difference between thefirst quasi carry amount P1 and the second quasi carry amount P2 is 2,in the case in which the unit carrying resolution X is sufficientlyfine, an effect equivalent to that of the embodiment can be achieved.That is, when the difference between the first quasi carry amount P1 andthe second quasi carry amount P2 is set to n, so far as X/n is highlyfine in contrast to the visibility limit resolution W, an effect of theinvention can be obtained. Further, even when a larger number of quasicarry amounts are selected randomly such as a third quasi carry amountP3 or a fourth quasi carry amount P4 other than the first quasi carryamount P1 and the second quasi carry amount P2, so far as the unitcarrying resolution X is sufficiently fine, an effect equivalent to thatof the above-described embodiments can be attained. However, it isnaturally the best that the difference between the first quasi carryamount P1 and the second quasi carry amount P2 is 1.

That is, it is preferable that the difference between the first quasicarry amount P1 and the second quasi carry amount P2 is the unitcarrying amount. In this way, a difference among the plurality of quasilogical carry amounts can be minimized. The difference is sensed as anerror in an accuracy of carrying the sheet in the sub-scanning directionand therefore, minimizing the difference signifies that deterioration inthe error can be reduced as less as possible and other trade-off factorcan be minimized.

Further, although according to step 152 in the second mode of theabove-described embodiments, it is determined whether the carry amount Tby which the sheet is to be carried is smaller than the second quasilogical carry amount P2, when smaller, the set carry amount R is setwith the first quasi carry amount P1 (step 153), when larger, the setcarry amount R is set with the second quasi carry amount P2 (step 154),the invention is not limited thereto. For example, the invention may beexecuted such that at step 152, it is determined whether the carryamount T by which the sheet is to be carried is smaller than the logicalcarry amount P, when smaller, the set carry amount R is set with thefirst quasi carry amount P1 at step 153, and when larger, the set carryamount R is set with the second quasi carry amount P2 at step 154.Further, the invention may be executed such that at step 152, it isdetermined whether the carry amount T by which the sheet is to becarried is larger than the first quasi carry amount P1, when larger, theset carry amount R is set with the first quasi carry amount P1 at step153, and when smaller, the set carry amount R is set with the secondquasi carry amount P2 at step 154. In either of the above-describedcases, the difference S between the carry amount T by which the sheet isto be carried and the set carry amount R does not exceed 1 [pulse].

Further, although according to the above-described embodiments, thedifference S between the carry amount T by which the sheet is to becarried and the set carry amount R is calculated at each time ofcarrying the sheet by one time (refer to step 158), the invention is notlimited thereto. For example, a difference between a carry amount bywhich a sheet is to be carried and a carry amount by which the sheet isactually carried may be calculated at a predetermined number of times ateach time of carrying the sheet by the predetermined number of times anda carry amount by way which the sheet is to be carried may be calculatedin carrying the sheet at a succeeding time and thereafter based on thedifference.

Next, an explanation will be given of an effect achieved by themultifunction machine 1, 80 according to the above-describedembodiments.

The inkjet printers 4, 70 according to the above-described embodimentsare controlled such that the sheet is carried by either of the pluralityof quasi logical carry amounts P1, P2 including the natural number P2larger than the logical carry amount P and the natural number P1 smallerthan the logical carry amount P and the sheet is recorded at each timeof carrying the sheet. Further, the carry amount of the sheet isdetermined to either of the quasi logical carry amounts of P1 or P2 suchthat the difference S between the carry amount by which the sheet isassumed to be carried by the logical carry amount P and the actual carryamount of the record medium R does not exceed 1 (unit carry amount).Therefore, the sheet can be recorded even when the recording resolutiond is not set to a multiple of the unit carrying resolution X of theencoder 67. As a result, high image quality recording can be realizedwithout using an encoder at high cost having a high resolution andwithout considerably reducing a recording speed.

Further, according to the inkjet printers 4, 70 according to theabove-described embodiments, the plurality of quasi logical carryamounts P1, P2 are set to the smallest natural number P2 larger than thelogical carry amount P and the largest natural number P1 smaller thanthe logical carry amount and therefore, a difference between the quasilogical carry amount P1 and the quasi logical carry amount P2 can beminimized. Therefore, a higher image quality recording can be realized.

Further, according to the inkjet printers 4, 70 of the above-describedembodiments, only when the logical carry amount P is not a naturalnumber, the sheet is carried by either of the quasi logical carry amountP1 or the quasi logical carry amount P2, and when the logical carryamount P is a natural number, a sheet is carried by the logical carryamount P. Therefore, the image quality can be prevented from beingdeteriorated when the logical carry amount P is a natural number.

Further, according to the inkjet printer 70 of the above-describedembodiments, ROM 73 is stored with a plurality of logical carry amountsP in a related manner to the recording resolutions d and previouslystored with the quasi logical carry amounts P1, P2 for the logical carryamount P of a nonnatural number. Therefore, a load of calculating thelogical carry amount P and the quasi logical carry amounts P1, P2 can bealleviated.

Further, when the recording resolution d is inputted from the keyboard66, the inkjet printer 4 according to the above-described embodimentscalculates the logical carry amount P in accordance with the inputtedrecording resolution d and calculates the quasi logical carry amountsP1, P2 in accordance with the inputted recording resolution d when thecalculated logical carry amount is a nonnatural number. Therefore, asheet can be recorded not only by the recording resolution d stored todefault but also by an arbitrary one of the recording resolution d.

Further, the inkjet printer 4 according to the above-describedembodiments determines whether the recording resolution d for thelogical carry amount P which is a natural number is equal to or largerthan 5,000[dpi], and permits to record the sheet only when the recordingresolution d is determined to be equal to or larger than 5,000 [dpi].Therefore, low image quality recording can be prevented from beingexecuted. The inkjet printer 4 according to the invention uses anencoder having a resolution of 7,000[dpi] which is equal to or smallerthan a distance corresponding to the visibility limit resolution.Therefore, even when the sheet is carried by either of the first quasilogical carry amount P1 and the second quasi logical carry amount P2,low image quality recording can be prevented from being executed.

The multifunction machine 1 of the above-described embodiment refers toa method of printing by increasing the recording resolution d in thesub-scanning direction by dividing a single piece of the main scanningline data L in the dot data by a plurality of pieces (5 pieces in theabove-described embodiment) of the divided line data L1 through L5 andforming lines corresponding to respectives thereof on the sheet. Thatis, in comparison with the case of forming a single piece of line on therecorded medium for each piece of line data L, a region of arrangingdots (record pixels) in the sub-scanning direction is increased.Thereby, even when positions of the dots are shifted in the sub-scanningdirection, a gap is difficult to be produced between the dots. As afactor of shifting the dots in the sub-scanning direction, there arepointed out an accuracy of fabricating the nozzle pitch, an accuracy ofa direction of delivering ink, an accuracy of scanning the recordinghead, an accuracy of carrying the record medium and the like. Thefactors emerge as noise which cannot be controlled by individualmachines, individual scanning timings and the like and therefore, theshift of the recording position of the dot in the sub-scanning directioncan be displayed as a probability of placing the dot as shown by FIG.17A.

Therefore, it is known that probability distributions densely overlapand a probability of producing a region at which dots are not overlappedbecomes lower in the case of the high recording resolution in thesub-scanning direction as shown by FIG. 17C in comparison with the casein which the recording resolution in the sub-scanning direction is lowas shown by FIG. 17B. When the probability of placing the dot becomes 0,it signifies that a color of a matrix of the record medium isnecessarily thin at the region and therefore, that the probabilitydistributions of placing the dots are densely overlapped as describedabove indicates that a white streak is difficult to be seen.

According to the above-described embodiment, a single piece of the mainscanning line data L is divided into 5 pieces of divided line data L1through L5, and the lines corresponding to the respectives thereof areformed on the record medium and therefore, the recording resolution inthe sub-scanning direction is multiplied by 5. Therefrom, theprobability of producing the white streak can be made to be low.Further, by taking an arbitrary value (for example, 2, 3, 4, 5, 6, 7, 8,9, 10 . . . ) for N, the effect can be achieved by a desired amount.

Therefrom, it seems that it is known to be able to improve the imagequality as desired by setting an arbitrary sub-scanning resolution.

Although the invention has been described according to theabove-described embodiments, the invention is not limited thereto.Various embodiments without deviating from the sprint and the range ofthe invention can be embodied.

1. An inkjet recording apparatus comprising: a recording head having anozzle row aligned with a plurality of nozzles for ejecting ink; acarrying mechanism being capable of carrying a record medium by amultiple of an arbitrary natural number of a unit carrying amount in adirection in parallel with the nozzle row; a carry controlling unit thatcontrols the carrying mechanism such that the record medium is carriedby any of a plurality of quasi logical carry amounts including a naturalnumber larger than a logical carry amount, which is determined based ona recording resolution along the direction in parallel with the nozzlerow and a number of nozzles that are used for recording in the nozzlerow and is indicated as a multiple of the unit carrying amount, and anatural number smaller than the logical carry amount; and a recordinghead controlling unit that controls the recording head such that therecord medium is recorded at each time of carrying the record medium bythe carrying mechanism that is controlled by the carry controlling unit;wherein the carry controlling unit determines a carry amount of therecord medium by the carrying mechanism from the plurality of quasilogical carry amounts such that a difference between a carry amount whenthe record medium is assumed to be carried by the logical carry amountand an actual carry amount of the record medium does not exceed apredetermined value.
 2. The inkjet recording apparatus according toclaim 1, wherein the plurality of quasi logical carry amounts include asmallest natural number larger than the logical carry amount and alargest natural number smaller than the logical carry amount.
 3. Theinkjet recording apparatus according to claim 1, wherein thepredetermined value is the unit carrying amount.
 4. The inkjet recordingapparatus according to claim 1, wherein the carry controlling unitcontrols the carrying mechanism such that the record medium is carriedby any of the plurality of quasi logical carry amounts only when thelogical carry amount is not a natural number and controls the carryingmechanism such that the record medium is carried by the logical carryamount when the logical carry amount is a natural number.
 5. The inkjetrecording apparatus according to claim 1, further comprising: a logicalcarry amount storing unit stored with each of a single or a plurality ofthe logical carry amounts in a related manner to the recordingresolution; and a quasi logical carry amount storing unit stored withthe plurality of quasi logical carry amounts for the single or theplurality of logical carry amounts stored to the logical carry amountstoring unit which is not a natural number.
 6. The inkjet recordingapparatus according to claim 1, further comprising: a logical carryamount calculating unit that calculates the logical carry amountcorresponding to the recording resolution when the recording resolutionis provided; and a quasi logical carry amount calculating unit thatcalculates the quasi logical carry amount corresponding to the recordingresolution when the logical carry amount calculated by the logical carryamount calculating unit is not a natural number.
 7. The inkjet recordingapparatus according to claim 1, wherein the unit carry amount is equalto or smaller than a distance corresponding to a visibility limitresolution.
 8. A recording method for use in an inkjet recordingapparatus including a recording head having a nozzle row aligned with aplurality of nozzles for ejecting ink, and a carrying mechanism beingcapable of carrying a record medium by a multiple of an arbitrarynatural number of a unit carry amount in a direction in parallel withthe nozzle row, the recording method comprising: carrying the recordmedium by a single or a plurality of times by the carrying mechanism byany of a plurality of quasi logical carry amounts including a naturalnumber larger than a logical carry amount, which is determined based ona recording resolution along the direction in parallel with the nozzlerow and a number of the nozzles that are used for recording in thenozzle row and is indicating a rate relative to the unit carry amount inthe carrying mechanism, and a natural number smaller than the logicalcarry amount; and recording the record medium by the recording headafter the carrying; wherein in the carrying, the record medium iscarried by a carry amount such that a difference between a carry amountby which the record medium is assumed to be carried by the logical carryamount and an actual carry amount of the record medium does not exceed apredetermined value.